Tic disorders, such as Tourette syndrome, are more common in children who have special educational needs, scientists have found.

Researchers from the University of Rochester School of Medicine in Rochester, New York, also found the disorders were more common in all children than previously thought.

Tourette syndrome patients suffer from twitches and tics, and are often prescribed strong tranquillisers which can reduce the twitching, but also dull the ability to think and slow down movements.

Tics are involuntary. They are brief, repetitive movements, which are either motor such as blinking or head jerking, or vocal such as throat clearing.

These tics may be a sign of an underlying brain developmental disorder that contributes to academic difficulties

Dr Roger Kurlan, University of Rochester School of Medicine

Tourettes is diagnosed once the tics have been present for at least a year.

The US researchers say it is important for teachers and parents to be on the look-out for tics in children, because symptoms can be treated and children's educational and social development could be improved.

Dr Roger Kurlan, who led the study, said: "These tics may be a sign of an underlying brain developmental disorder that contributes to academic difficulties."

High levels

The team interviewed 1,596 schoolchildren in Rochester and the surrounding area.

Of those in special education classes, 27% had tics, compared to 20% in mainstream classes.

Eight per cent of children in the special education classes met the diagnostic criteria for Tourettes compared to 3% of children in mainstream classes.

The researchers said both sets of figures were higher than had been seen previously.

Tourette syndrome is linked to abnormalities in the basal ganglia in the brain, which controls movement.

Conditions such as attention deficit hyperactivity disorder, obsessive compulsive disorder and some learning disabilities are also linked with abnormalities in the area.

Patients with Tourettes often have one of more of these conditions.

Dr Kurlan said: "While most cases of tics are mild and eventually resolve on their own, in some cases tics may be a first sign of an underlying disturbance in basal ganglia development which in turn, can lead to Tourette syndrome or one of these disorders that can interfere with success at school.

Monitoring

"It may be important to train physicians, teachers and parents to recognise tics early in young children, because they may benefit from early intervention, or at least careful monitoring."

The researchers say, unlike previous studies which have been based on medical records, this study used direct examination.

They say many of the cases were mild and had not been seen by health professionals. Sometimes, even the sufferer is unaware of the tic.

Dr Kurlan said there could have been an element of self-selection in the study, with more parents who suspected their children had tics consenting to take part.

But he said the findings still showed previous numbers of cases had been underestimated.

Dr High Rickards, a medical advisor to the UK Tourette Syndrome Association, said: "This is saying 3% of people in regular education have Tourettes. That matches a UK study."

But he questioned the link made between learning difficulties and Tourettes.

"It might well be people with Tourettes have a variety of learning disabilities, but it is difficult to establish the exact causal relation between the two.

The research was published in Neurology, the journal of the American Academy of Neurology.